Radiation-induced pollen abortion in several commelinaceous taxa: Its relation to chromosomal parameters

Abstract

The effects of x or gamma rays and 0·43-MeV neutrons on pollen abortion, as measured by cotton blue staining, were studied in fifteen members of four genera ( Floscopa, Gibasis, Tradescantia and Tripogandra ) of the family Commelinaceae. The roles of interphase chromosome volume (ICV), nuclear volume (NV) and ploidy on the degree of pollen abortion induced by radiation were investigated. For each species, the maximum percentage of aborted grains was determined over a postirradiation period equivalent to an entire period of microsporogenesis. Dose-response curves were constructed for each species and these were found to vary in slope. From these curves, RBE values were determined for two species of Tradescantia and for a diploid and tetraploid species of Gibasis . Within the dose range investigated, highest RBEs at 10 per cent pollen abortion ranged from about 23 for Gibasis karwinskyana (4x) to about 9×4 for the diploid Gibasis . Ploidy was not found to influence the radiation response to an appreciable extent when ICVs were similar. High polyploids with small ICVs were found to be more radioresistant, but this response appears to be a function of ICV and not the degree of ploidy. Correlations were sought between 50 per cent pollen abortion and ICV or NV. No correlations were found using NV. However, following low LET radiation an inverse relationship (−1 slope) was obtained between 50 per cent pollen abortion and ICV. The same relation appears to hold for neutrons, but since only four species were available for comparison this relationship is still inconclusive.